Electric power steering apparatus

Abstract

In an electric power steering apparatus, a control unit includes: a power module that is in surface contact with a heatsink, and in which a plurality of switching elements are mounted internally; a holder that places the power module in close contact with the heat sink, and that also positions the power module; and a controlling circuit board that is disposed so as to be separated axially from the holder, and on which a central processing unit (CPU) is mounted; and the power module is disposed on a first surface of a first side of the holder, and a circumferential surface of a capacitor that suppresses electric power supply pulsation is disposed so as to be in close contact with a capacitor recess portion that is formed on a second surface of a second side of the holder.

The invention claimed is: 
     
       1. An electric power steering apparatus in which a control unit that controls driving of an electric motor is disposed so as to be coaxial to an output shaft of said electric motor, and in which said control unit and said electric motor are integrated, wherein:
 said control unit comprises:
 a power module that is in surface contact with a heatsink, and in which a plurality of switching elements are mounted internally, said power module controlling electric power that is supplied to said electric motor; 
 a holder that places said power module in surface contact with said heatsink, and that also positions said power module; and 
 a controlling circuit board that is disposed so as to be separated axially from said holder, and on which a central processing unit (CPU) that controls driving of said electric motor is mounted; and 
 
 said power module is disposed on a first surface of said holder, and a circumferential surface of a capacitor that suppresses electric power supply pulsation is disposed so as to be in surface contact with a capacitor recess portion that is formed on a second surface of said holder. 
 
     
     
       2. The electric power steering apparatus according to  claim 1 , wherein an electric power supply system busbar that is embedded in said holder comprises a step in which a portion that is near said capacitor is closer to said heatsink than a portion that is near said power module. 
     
     
       3. The electric power steering apparatus according to  claim 2 , wherein said busbar is electrically connected to each of an electric power supply terminal of said power module and a capacitor terminal of said capacitor. 
     
     
       4. The electric power steering apparatus according to  claim 3 , wherein said busbar is electrically connected to said electric power supply terminal in a space between said holder and said controlling circuit board, and said busbar is electrically connected to said capacitor terminal inside or at a front surface of said holder. 
     
     
       5. The electric power steering apparatus according to  claim 1 , wherein a module recess portion with which said power module is placed in surface contact is formed on said holder. 
     
     
       6. The electric power steering apparatus according to  claim 1 , wherein a protruding portion that is placed in contact with said power module is formed on said holder. 
     
     
       7. The electric power steering apparatus according to  claim 1 , wherein a wall portion that is placed in contact with an edge portion of a molded body in which said plurality of switching elements are mounted internally, and that positions said power module, is formed on said holder. 
     
     
       8. The electric power steering apparatus according to  claim 1 , wherein a post that spaces apart and holds said holder and said controlling circuit board is disposed between said holder and said controlling circuit board. 
     
     
       9. The electric power steering apparatus according to  claim 1 , wherein a contacting portion that protrudes toward said heatsink and is placed in contact with said heatsink is formed on a circumferential edge portion of said holder, and a gap is formed between said holder and said heatsink. 
     
     
       10. The electric power steering apparatus according to  claim 1 , wherein:
 a non-output end bearing that rotatably supports said output shaft is disposed on a central portion of said heatsink; 
 said power module, said holder, and said controlling circuit board that are stacked sequentially from said heatsink are sealed by a case that has a plane of a cylindrical cup shape that has an end surface that is placed in contact with an outer circumferential edge portion of said heatsink; and 
 a connector that is electrically connected to said control unit, and that extends so as to be parallel to said output shaft, is disposed within said plane of said case. 
 
     
     
       11. The electric power steering apparatus according to  claim 1 , wherein:
 an output end bearing is disposed on a central portion of said heatsink so as to rotatably support said output shaft, which passes through said heatsink; 
 said power module, said holder, and said controlling circuit board that are stacked sequentially from said heatsink are sealed by a tubular case that has a first end surface that is placed in contact with an outer circumferential edge portion of said heatsink, and a second end surface that is placed in contact with an end surface of a bracket of said electric motor; and 
 a connector that that is disposed alongside an outer circumferential surface of said case is electrically connected to said control unit radially outside said case. 
 
     
     
       12. The electric power steering apparatus according to  claim 1 , wherein said switching elements of respective phases of said power module are embedded in a single molded body. 
     
     
       13. The electric power steering apparatus according to  claim 1 , wherein said switching elements of respective phases of said power module are embedded in separate molded bodies, and said power modules for each of said phases are disposed in a radial pattern so as to point toward said output shaft. 
     
     
       14. An electric power steering apparatus in which a control unit that controls driving of an electric motor is disposed so as to be coaxial to an output shaft of said electric motor, and in which said control unit and said electric motor are integrated, wherein:
 said control unit comprises:
 a power module that is in surface contact with a heatsink, and in which a plurality of switching elements are mounted internally, said power module controlling electric power that is supplied to said electric motor; 
 a holder that places said power module in surface contact with said heatsink, and that also positions said power module; and 
 a controlling circuit board that is disposed so as to be separated axially from said holder, and on which a central processing unit (CPU) that controls driving of said electric motor is mounted; and 
 
 said power module is disposed on a first surface of said holder, and a circumferential surface of a capacitor that suppresses electric power supply pulsation is disposed so as to be in surface contact with a capacitor recess portion that is formed on said first surface of said holder, wherein said first surface includes different relative elevations in relation to the controlling circuit board. 
 
     
     
       15. The electric power steering apparatus according to  claim 14 , wherein an electric power supply system busbar that is embedded in said holder comprises a step in which a portion that is near said capacitor is closer to said controlling circuit board than a portion that is near said power module. 
     
     
       16. The electric power steering apparatus according to  claim 15 , wherein said busbar is electrically connected to each of an electric power supply terminal of said power module and a capacitor terminal of said capacitor. 
     
     
       17. The electric power steering apparatus according to  claim 16 , wherein said busbar is electrically connected to said electric power supply terminal in a space between said holder and said controlling circuit board, and said busbar is electrically connected to said capacitor terminal inside or at a front surface of said holder. 
     
     
       18. The electric power steering apparatus according to  claim 14 , wherein a module recess portion with which said power module is placed in surface contact is formed on said holder. 
     
     
       19. The electric power steering apparatus according to  claim 14 , wherein a protruding portion that is placed in contact with said power module is formed on said holder. 
     
     
       20. The electric power steering apparatus according to  claim 14 , wherein a wall portion that is placed in contact with an edge portion of a molded body in which said plurality of switching elements are mounted internally, and that positions said power module, is formed on said holder. 
     
     
       21. The electric power steering apparatus according to  claim 14 , wherein a post that spaces apart and holds said holder and said controlling circuit board is disposed between said holder and said controlling circuit board. 
     
     
       22. The electric power steering apparatus according to  claim 14 , wherein a contacting portion that protrudes toward said heatsink and is placed in contact with said heatsink is formed on a circumferential edge portion of said holder, and a gap is formed between said holder and said heatsink. 
     
     
       23. The electric power steering apparatus according to  claim 14 , wherein:
 a non-output end bearing that rotatably supports said output shaft is disposed on a central portion of said heatsink; 
 said power module, said holder, and said controlling circuit board that are stacked sequentially from said heatsink are sealed by a case that has a plane of a cylindrical cup shape that has an end surface that is placed in contact with an outer circumferential edge portion of said heatsink; and 
 a connector that is electrically connected to said control unit, and that extends so as to be parallel to said output shaft, is disposed within said plane of said case. 
 
     
     
       24. The electric power steering apparatus according to  claim 14 , wherein:
 an output end bearing is disposed on a central portion of said heatsink so as to rotatably support said output shaft, which passes through said heatsink; 
 said power module, said holder, and said controlling circuit board that are stacked sequentially from said heatsink are sealed by a tubular case that has a first end surface that is placed in contact with an outer circumferential edge portion of said heatsink, and a second end surface that is placed in contact with an end surface of a bracket of said electric motor; and 
 a connector that that is disposed alongside an outer circumferential surface of said case is electrically connected to said control unit radially outside said case. 
 
     
     
       25. The electric power steering apparatus according to  claim 14 , wherein said switching elements of respective phases of said power module are embedded in a single molded body. 
     
     
       26. The electric power steering apparatus according to  claim 14 , wherein said switching elements of respective phases of said power module are embedded in separate molded bodies, and said power modules for each of said phases are disposed in a radial pattern so as to point toward said output shaft.